摘要:

Published data for spiders were analyzed to find out if the increment in size at molt (Dyar's constant) of spiders approached 28% as if each instar acts as an ecologically isolated form. Size increments of roughly 20% were found in small, actively hunting spiders, 25% in sallying predators which use no web or use only the upper surface of a web, and 30% for araneid and theridiid species which use the lower surface of a web; the highest value found for Dyar's constant was in an ambushing, thomisid species. Larger species of spiders have more instars, have larger values for Dyar's constant, and also seem to be less active foragers than smaller species. Published data for insects revealed that grazing holometabolous insects have the largest growth increments, and insects which hunt for food as immatures have lower values, the range from ca. 60% to ca. 20%.Lower “freight” costs and more constant agility (power/wt ratio) are mechanical advantages associated with low Dyar's constant–the implications of this for animals with continuous growth are discussed. Data on growth increments of both spiders and insects may be better explained by convergent evolution resulting from the need for agility during hunting than by Juberthie's (1955) idea of phylogenetically significant growth increments. Finally, the coexistence of species of lycosid-like spiders is discussed in relation to phenology, size and habitat; anr-adapted species of the genusPardosa(Lycosidae) has the same increment at the molt as a relatedK-selected species, but uses fewer instars and smaller size to achieve rapid population growth in its distinct habitat.

ISSN:1754-5692    

DOI:10.1093/ee/5.1.1

出版商:Oxford University Press    

年代:1976

数据来源: OUP

摘要:

Mathematical models describing losses of lodgepole pine (Pinus contorta var. latifoliaEngelmann) and survival of mountain pine beetle (Dendroctonus ponderosaeHopkins) by life stage were prepared from data covering a 13-yr period. The greatest survival and emergence of beetles/unit area of bark occurred in trees of large diameter. After most trees of large diam were killed, gallery starts and egg production continued to increase. However, larval survival declined and emergence returned to the endemic level. At high densities of gallery starts and inches, beetle survival was low, probably because of excessive competition among larvae and drying of phloem. Under these conditions of stress, the sex ratio appears to shift further in favor of ♀ after most of the large trees are killed. These observations demonstrate the close association of beetle dynamics with diam structure of lodgepole pine stands, and support the theory that epidemics are strongly dependent upon the presence of large trees having thick phloem.

ISSN:1754-5692    

DOI:10.1093/ee/5.1.11

出版商:Oxford University Press    

年代:1976

数据来源: OUP

摘要:

Extension entomologists traditionally have faced the problem of collecting, integrating, and reporting data relevant to agriculture with only crude information processing capabilities at their disposal. This paper discusses the use of computer-based extension delivery systems to augment the flows of information in a modern pest management implementation program. The paper identifies the needs and constraints associated with an integrated pest management (IPM) data acquisition/delivery system developed for pests of apples and other crops in Michigan. The fact that these needs impel a reassessment of customary extension entomology methods is emphasized. Examples of information application types including biological data, weather data, pest population and management models, memoranda, reference data, system documentation, and educational or performance evaluation programs are given. A computer-based Pest Management Executive System (PMEX) is presented. The system consists of a central computer with appropriate software and a telecommunications network linking extension offices scattered over a wide area. At these sites, remote data terminals are used to update and interrogate a large data-base associated with on-line pest management. The implications of prototype IPM extension systems in this class as opposed to extension delivery systems in general are discussed.

ISSN:1754-5692    

DOI:10.1093/ee/5.1.20

出版商:Oxford University Press    

年代:1976

数据来源: OUP

摘要:

Three aspects of the biology ofCerotoma trifurcata(Forster), the bean leaf beetle, were studied: 1) the seasonal occurrence of adults and eggs in soybean fields, 2) the occurrence of adults and eggs on plants other than soybean, and 3) the effects on beetle populations of varying the phenology of the soybean.There are 3 peaks of adult abundance in central Illinois soybean fields; the arrival of overwintering adult colonizers and the 2 summer generations. The colonizers arrive shortly after soybean emergence in late May or early June and die after depositing eggs in the soil near the plants. First generation adults, present from mid or late July until the 2nd or 3rd wk of August, also oviposit and then die. Second generation adults are abundant in September and leave the fields when the plants are senescent. They eventually move to overwintering sites and do not oviposit until the following spring. Peak egg abundance always occurred later than peak adult abundance.Before soybeans emerged we found active adults but no eggs in alfalfa fields. Alfalfa may be an important interim food for adults in spring. We found eggs in the soil near 3 native wild Leguminosae,Desmodium illinoenseGray,D. cuspidatum(Muhl.), andStrophostyles helvola(L.).Changes in the phenological relationship between the soybean and the bean leaf beetle affect the duration of the plants' exposure to beetle injury, and may also have a significant effect on beetle population size. In Illinois, soybeans usually mature early enough to escape most defoliation by 2nd generation adults. Late planted fields escape the colonizers. General late planting over a large area can result in a great decrease in bean leaf beetle populations since, in the absence of their most abundant food plant most adults apparently die without ovipositing or at least without ovipositing on a suitable larval host.

ISSN:1754-5692    

DOI:10.1093/ee/5.1.35

出版商:Oxford University Press    

年代:1976

数据来源: OUP

摘要:

Phytophagous insects representing 5 orders, 32 families, and 89+ species are reported as comprising the insect fauna ofAmbrosia dumosa(Gray) Payne (Compositae) in southern California. Most insects found attacking this native ragweed were euryphagous, ectophagous, sap- and foliage-feeding species. About ½ reproduced on this plant. Twenty-one (46%) of the 46 associates identified to species were stenophagous, their hosts apparently confined to the tribe Heliantheae. Only 5 (11%) of these were minor or major pests of cultivars.

ISSN:1754-5692    

DOI:10.1093/ee/5.1.45

出版商:Oxford University Press    

年代:1976

数据来源: OUP

摘要:

Codling moth (Laspeyresia pomonella) egg and 1st instar larval mortality was evaluated during 1970–1971 on ‘Bartlett’ pear in southern Oregon. Average egg mortality was 20 and 33% in 1970 and 1971 respectively. Parasitism byTrichogramma minutumRiley accounted for 10% of the total. Mortality to 1st instar larvae averaged 55% and total egg-1st instar mortality 69% for the 2-yr period. Favored sites for oviposition on pear were the lower surface of fruit cluster leaves; 80–90% of the fruit entries were through the calyx or beneath the calyx lobes. Susceptibility of various pear cultivars to entry by the first instar larvae was compared to the Golden Delicious apple variety. A moderate to high degree of antibiosis was detected in the D'Anjou, Bosc and Comice cultivars. This resistance is believed related to lignification and formation of stone cells which prevent or hamper larval entrance into the fruit.

ISSN:1754-5692    

DOI:10.1093/ee/5.1.51

出版商:Oxford University Press    

年代:1976

数据来源: OUP

摘要:

Mortality and developmental rates of the cotton fleahopper,Pseudatomoscelis seriatus(Reuter), were affected by the species and maturity of host plants. Survival was higher and development was faster onCrotonsp. than on other hosts such as spotted beebalm,Monarda punctataL., cutleaf primrose,Oenothera laciniataHill, and cotton,Gossypium hirsutumL. Also, survival and development rates were higher on flowering plants than on plants in a preflowering growth stage.Predictions of fleahopper development based on temperature data were affected by the host plant. Heat units required for total nymphal development varied from 98.2°C days on flowering croton to 163.2°C-days on preflowering cutleaf primrose.

ISSN:1754-5692    

DOI:10.1093/ee/5.1.55

出版商:Oxford University Press    

年代:1976

数据来源: OUP

摘要:

Biological and ecological studies showed that the potato scab gnat,Pnyxia scabiei(Hopkins), long considered the causative agent of deep-pitted scab, is primarily a fungus-feeding gnat. It does not feed on healthy tissue of potato tubers and is not the causative agent of deep-pitted scab.

ISSN:1754-5692    

DOI:10.1093/ee/5.1.59

出版商:Oxford University Press    

年代:1976

数据来源: OUP

摘要:

Populations of phytoseiid mites on apple foliage were studied in a natural (unsprayed) and 2 artificial (captan and DDT-captan) environmental blocks in a “Northwestern Greening” apple orchard in Door Co., Wisconsin, from 1959 through 1962. Twelve species of phytoseiids were found of whichTyphlodromus caudiglansSchuster,Amblyseius fallacis(Garman),Typhlodromus longipilisNesbitt, andAmblyseius zwoelferi(Dosse) were the most common in that order.T. caudiglanswas far the most common species annually in the check and captan blocks andA. fallacisin the DDT-captan. The latter species' tolerance to DDT increased annually.

ISSN:1754-5692    

DOI:10.1093/ee/5.1.63

出版商:Oxford University Press    

年代:1976

数据来源: OUP

摘要:

An aqueous mixture of trimethylamine, ammonia, linoleic acid, and indole acidified topH 6 with acetic acid attracts the eye gnatHippelates collusor(Townsend). To study the influence of structural modifications of these active components on attractancy, we bioassayed homologs and analogs of the against field populations of the insects. Primary and secondary aliphattc amines either decreased or did not influence the attractancy of a composition containing ammonia, linoleic acid, and indole acidified with acetic acid topH 6. With the exception of tripropylamine, all tertiary amines tested enhanced the attractancy of the composition. Cyclic amines reduced it.When a low-molecular aliphatic carboxylic acid was used to aCidify a composition containing trimethylamine, ammonia, linoleic acid, and indole topH 6, those acidified with acetic, propionic, orn-butyric acid showed the greatest attractancy.The addition of linoleic or oleic acid to a composition containing trimethylamme, ammonia, and indole acidified topH 6 with acetic acid increased the activity of the composition. Saturated fatty acids usually lowered it. Among unsaturated fatty acids tested, only those having 18 carbon atoms with acisdouble. bond at the 9 positon or 2cisdouble bonds at the 9 and 12 positions were effective in increasing the activity.

ISSN:1754-5692    

DOI:10.1093/ee/5.1.65

出版商:Oxford University Press    

年代:1976

数据来源: OUP